Plastic cap for stoppering bottles

ABSTRACT

The invention concerns plastic seals or caps for stoppering bottles. The skirt of these caps is obtained by coextrusion or thermoshaping of two plastic materials of the same family. The inside layer contains an additive which reduces the rubbing factor, while the outside layer may have different characteristics.

United States Patent [191 [11] 3,920,143 Vouillemin 5] Nov. 18, 1975 PLASTIC CAP FOR STOPPERING BOTTLES Inventor: Jean-Marie Vouillemin,

Foreign Application Priority Data June 12, 1974 Luxemburg 70300 US. Cl. 215/307; 215/317; 2l5/DIG. 2 Int. Cl. B65D 41/22 Field of Search 215/230, 277, 307, 316,

215/31'7, DIG. 2

References Cited UNITED STATES PATENTS [/1975 Kovac 215/317 FOREIGN PATENTS OR APPLICATIONS 957,333 5/1964 United Kingdom 2l5/3l7 Primary ExaminerDonald F. Norton Attorney, Agent, or Firm-Dennison, Dennison, Meserole & Pollack [57] ABSTRACT The invention concerns plastic seals or caps for stoppering bottles. The skirt of these caps is obtained by coextrusion or thermoshaping of .two plastic materials of the same family. The inside layer contains an additive which reduces the rubbing factor, while the outside layer may have different characteristics.

5 Claims, 2 Drawing Figures US. Patent Nov. 18,1975 3,920,143

PLASTIC CAP FORSTOPPERING BOTTLES The present invention concerns a plastic cap for stoppering bottles.

In order that these caps fulfilltheir role, that is primarily to protect the corks from any deterioration or other violation, they must be fixed on the neck of the bottle in an immovable way. This result is obtained by the choice of a top made of an elastic substance which has sufficient resistance to support strong radial traction and with the inner diameter of the skirt of the cap, before it is put into place, being less than the smallest exterior diameter of the part of the neck of the bottle that is designed to cap.

In order to position the cap, a device is used possessing a certain number of prongs with rounded exterior surface, which are mounted on slides, each one on a support, in such a way as to be able to spread apart radially one from the other, which serves to dilate the skirt sufficiently to permit the penetration of the neck of the bottle between the prongs and by continuing the movement of the bottle in the same direction, the disengagement of the cap, which automatically resumes its initial dimensions, which causes it to adapt itself closely to the exterior surface of the neck of the bottle. As the bottle neck normally terminates in a rim around the bottle opening, the tension of the plastic will be strongest in this area and it becomes impossible to remove the cap without tearing it.

This type of capping has already been used by individual bottlers, but for large scale production it presents a problem which has until 1 now not been surmounted since the prongs which spread open the cap exert considerable force. The force brought into play is all the greater as the full extent is reached imperatively without exceeding the limit of elasticity inherent in the material. The force applied on the rounded surface of the prongs (the total peripheral surface of which is almost equal to that of the inner surface of the skirt) creates a friction force against the plastic. This friction force is maximal when in the final positioning the .prongs are separated from the cap.

In the present state of technology, even for average rates,-(less than 1,800 units per hour) of sealing bottles The skirts of existing caps of nominal diameter of 27.5

mm suitable for rims of 29 mm do not withstand, with- .out damage, dilation in several tenths of a second to a diameter of 42 mm (the required diameter for placement on rims of 34 mm).

In spite of a judicious choice of the nature of thesteel surface of the prongs on the one hand and of the plastic on the other, the rate of sealing theoretically possible cannot be attained without heating the metal which ends up by ruining the caps.

To reduce the rubbing factor between the cap and the prongs, one can add an additive to the plastic, but

this modification has a drawback; it becomes impossi- 2 decorating procedures such as offset, silk screen or any other process.

In addition, the extensibility of the caps is greatly improved. To this end, the superimposed plastic cap for stoppering, designed according to this invention, is formed by two elements: a cylindrical skirt and a disc attached to the edge of one of the openings of this cylinder, the skirt being formed by coextrusion of two thermoplastic materials of the same family with the inner layer containing, as an additive, a product which reduces the rubbing coefficient.

This over-sealcan also be formed by thermoshaping beginning with composite sheets obtained by coextrusion of two plastic materials of thesame family.

The additive can be'aimonostearate of glycerine for example or a fatty starch.

This invention will be illustrated in the following specification by several examples and the attached drawings in which:

FIG. 1 represents a vertical section of a cap according to the invention.

FIG. 2 represents an enlargement of a detail of the side of the skirt indicated by n in FIG. 1.

The skirt 1 is essentially cylindrical, only its upper edge 2 being slightly curved toward the inside in order to be joined to the disc 3 which forms the head of the cap: the joining of these two parts can be done by any known process, for example, casting from existing molds. The disc 3 can be provided with an opening 4 allowing the air to escape the moment the cap is placed on the bottle, I

The diameter d of the skirt is less than the smallest diameter of the neck of the bottle on which it is to be placed'and is constant throughout the entire height h below its upper edge. As can be seen more in detail on FIG. 2, the side of the skirt 1 is made of two layers 5 and 6 of ostensibly equal thickness, effected by coextrusion, layer 5 being on the inside and layer 6 on the outside. The two layers are closely joined, their surfaces of contact practically disappearing by the interpenetration of the molecules of their surfaces.

The composition of these layers which together form a thickness of 0.5 mm is notably the same, for example, high pressure low density polyethylene of grade 0.4. There has been added to the mass of the inner layer a slippery agent which reduces the rubbing factor of this layer. In one example, this agent is composed of 0.25% monostearate of glycerine.

In a second example, a fatty starch is added, preferably in the form of a chiefly nutritive substance, that is to say composed of elements which are non-toxic and non-alterable when in contact with alimetary products submerged in a neuter mass, the proportion of the mixture used being 2.5%.

Caps made in this way can be placed on the bottles at a much higher rate, more than 2400 units per hour. Yet imprinting the outside surface no longer presents a problem and can be done in the same way as ordinary caps.

There are also additional advantages of production according to this invention. Thus the two layersof the skirt can be of two different colors with a third color for the disc 3. It has been found that the use .of polyethylene of grade 0.4 almost completely eliminates the risk of cracking the caps during the period of stockpiling, whereas caps obtained by injection use materials of grade 3 or more.

in addition, agents added to the inner layer are in time diffused into the mass of the two layers, which again increases the rubbing coefficient inside the cap and contributes to the latter holding better on the neck of the bottle. This change does not become noticeable until several months after the manufacturing of the cap, imprinting and positioning having been completed for a long time.

Finally, coextrusion produces skirts with very improved mechanical characteristics: compared with a similar cover obtained by the usual extrusion method, extension of the breaking point goes from 460 to 588%, while constraint of the breaking point goes from l,l08 kg/cm to 1,662 kg/cm Thus the skirt ofa cap of nominal diameter of 27.5 mm can be dilated without damage in several tenths of a second to a diameter of 42 mm. Such a cap produced in accordance with this invention allows capping all bottles whose necks have rims ranging in diameter from 29 to 34 mm at a rapid rate (more than 2400 units per hour).

I claim:

1. A plastic cap for stoppering bottles and the like comprising a cylindrical plastic skirt open at both ends, a circular disc secured within one of said openings to close said one end, the body of said skirt having an inner and an outer layer being formed by the coextrusion of two thermoplastic materials of the same family, the inner layer of the skirt containing an additive which reduces the rubbing factor.

2. A cap as defined in claim 1, wherein the additive is monostearate of glycerine.

3. A cap as defined in claim 1, wherein the additive is a fatty starch.

4. A cap as defined in claim 1 wherein the skirt is formed by thermoshaping of composite sheets obtained by the coextrusion of two thermoplastic materials.

5. A cap as defined in claim 1, and further including an air escape opening in said disc. 

1. A plastic cap for stoppering bottles and the like comprising a cylindrical plastic skirt open at both ends, a circular disc secured within one of said openings to close said one end, the body of said skirt having an inner and an outer layer being formed by the coextrusion of two thermoplastic materials of the same family, the inner layer of the skirt containing an additive which reduces the rubbing factor.
 2. A cap as defined in claim 1, wherein the additive is monostearate of glycerine.
 3. A cap as defined in claim 1, wherein the additive is a fatty starch.
 4. A cap as defined in claim 1 wherein the skirt is formed by thermoshaping of composite sheets obtained by the coextrusion of two thermoplastic materials.
 5. A cap as defined in claim 1, and further including an air escape opening in said disc. 